Telephone system



July 17, 1928. 1,677,325

. H. 'voN BEC'KERATH TELEPHONE SYSTEM Filed April 30, 1927 a1 Le, l lle1 .fl a2 v i 5% as -1 (T 1 11:

Patented July 17, 1928.

' Y UNITED STATES PATENT orrice.

HANS VON BECKERATH, OF BERLIN, GERMANY, ASSIGNOR TO SIEMENS 8a HALSKE AK- TIENGESELLSCI-IAFT, OF SIEMENSSTADT, NEAR BERLIN, GERMANY.

TELEPHONE SYSTEM.

Application filed April 30, 1927, Serial No. 187,812, and in Germany November 25, 1926.

The invention relates to a circuit arrangement for receiving alternating current impulses, which are used especially in telephone systems for signalling, and for positioning and controlling selectors.

In such systems the alternating current relay which received the current impulses lies in bridge to the speaking wires at the incoming end of the speaking leads. During the further building up of the connection these speaking wires are in different ways closed to a circuit which is passable for alternating current by the direct current line relays, toroidal repeating coils, and condensers. Thus there is a shunt to the alternating current relay so that a portion of the incoming alternating current energy is uselessly consumed.

It is now the purpose of the invention to plished by arranging blocking circuits tuned to the frequency of the alternating current, behind the impulse receiving relays at the incoming end of a junction line over which these relays are actuated.

The drawing shows an example of the invention.

The figure shows a junction line VI and VI inductively coupled at both ends to the switching devices. Arranged at the outgoing end of this junction line is an impulse repeater of which simply the repeating relay A is shown. In shunt to the incoming speaking leads are two windings I and II of an alternating current relay W in series each with a condenser C and C In order to describe the mode of operation of this arrangement it is assumed that the junction line has been engaged in known manner by a group selector. For positioning the selectors at the incoming end of the junction line, the relay A is energized for each impulse to be transmitted, this relay applying the source of alternating current Q, to the left winding of the repeating coil U6 over its contacts a and a The alternating impulses are then passed on over the wires VI and VI of the junction line and through the repeating coil U6 to the impulse receiving relay. The condensers C and C connected in circuit with the winch ings I and II of the relay IV are soproportioned that the currents flowing through these windings have a phase displacement of about 90. In this way reliable functionavoid such energy losses, this being accom-v ing of the relay W is ensured. Blocking circuits are now inserted inthe continuing. speaking leads a and I) so as to restrictthe total incoming alternating current energy to the relay W. These blocking circuits consist of a condenser C and a choke coil D and a condenser. D and a choke coil D and are tuned to the frequency of the alternating current source Q. The incoming alternating currents thus have their path beyond the leads a and 6 blocked by these blocking circuits. Moreover these blocking circuits are so proportioned that they produce no damping on the speech current which has a considerably higher frequency than thesource of alternating current Q. I

What I claim is:

1. In a telephone system, a trunk line, means for transmitting alternating current impulses over said trunk line, an alternating current relay bridged across said trunk line at the distant end for receiving said impulses and for repeating them to a switching device for extendingthe trunk line, a blocking circuit inserted in each trunk conductor between the said. relay and said switching device, and means for tuning each blocking circuit to the frequency of said alternating current.

2. In a telephone system, an impulse repeater including a pair of talking conductors having electrically connected incoming and outgoing ends, a relay bridged across the conductors at the outgoing end, means for transmitting alternating current over the outgoing ends of the conductors for operating the relay, means controlled by the relay for repeating current over the incoming ends of the conductors, and means comprising a parallel resonant circuit tuned to the frequency of the alternating. current and connected in series with each of said talking conductors at a point intermediate the incoming end of the conductors and the relay, for preventing said alternating current from being transmitted over the incoming conductors.

3. In a telephone system, an impulse repeater having electrically connected outgoing and incoming conductors, a relay controlled by groups of digit impulses of alternating current received over the outgoing conductors, means controlled bythe relay for successively extending the incoming conductors responsive to each group of impulses, and means for preventing the alter-- nating current impulses from being weakened by being partially transmitted over the incoming conductors, said last means comprising parallelresonant circuit tuned to the frequency of the alternating current and connected in series With one of the incoming conductors at a point between the relay and the incoming end of the conductors,whereby transmission of the alternating current impulse over the incoming end of the conductors is prevented. W a I In Witness whereof, I" hereunto subscribe my name this 6th day of April, A. D. 1927.

HANS VON BECKERATH. 

